Method and system utilizing a percentage-based atrio-ventricular delay adjustment

ABSTRACT

A method and device for dynamic device based AV delay adjustment are provided. The method provides electrodes that are configured to be located proximate to an atrial (A) site and a right ventricular (RV) site. The method utilizes one or more processors, in an implantable medical device (IMD), for detecting an atrial paced (Ap) event or atrial sensed (As) event. The method determines a measured AV interval corresponding to an interval between the Ap event or the As event and a ventricular sensed event and calculates a percentage-based (PB) offset based on the measured AV interval. The method automatically dynamically adjusting an AV delay, utilized by the IMD, based on the measured AV interval and the PB offset and manages a pacing therapy, utilized by the IMD, based on the AV delay after the adjusting operation.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 62/734,830, filed Sep. 21, 2018, the entire disclosure of which isincorporated by reference herein.

FIELD OF THE INVENTION

Embodiments herein generally relate to implantable medical devices, andmore particularly to adjusting atrioventricular delay based on apercentage based offset derived from measured AV interval.

BACKGROUND OF THE INVENTION

Advances in implantable medical devices (IMD) and left ventricular (LV)lead design has improved electrical stimulation, delays, and pacing,resulting in a better patient outcome. Loss of atrioventricular (AV)electrical and mechanical synchrony can result in inadequate ventriculardepolarization, leading to suboptimal therapy. Optimal AV delay (AVD)can improve electrical synchrony by fusing an intrinsic conductionwavefront and device pacing to produce an enhanced depolarization of theventricles and increased cardiac output.

Cardiac resynchronization therapy (CRT) has been shown to improvehemodynamics in heart failure (HF) patients, particularly when the AVDhas been individualized for each patient. AVD programming for eachpatient is commonly performed in-clinic at implant, when an AVD isselected for each patient based on echocardiographic, ECG, or bloodpressure metrics. This one-time, static AVD selection does not accountfor short-term changes (hourly; e.g., exercise, sleep) or long-termchanges (monthly; e.g., disease progression) in a patient'selectromechanical conduction after the patient leaves the clinic.

At least one approach has been proposed that adjusts the AVD over time.In this conventional approach, an AV interval (AVI) is measured and theAVD is set to equal the AV interval reduced by a fixed amount that theclinician programs. Unfortunately, this conventional algorithm has twodrawbacks. First, the method of the AVD value simply subtracts a staticvalue (e.g., 50 ms). However, the cardiac conduction velocity, and thusthe intrinsic AV conduction interval, is heart rate dependent. Fasterheart rates are typically associated with shorter AV conductionintervals.

The second drawback of the conventional algorithm is that theinterventricular (i.e., RV-LV) timing is not adequately addressed. Whilemost users opt for the default “near-simultaneous” RV-LV biventricularpacing, providing simultaneous RV-LV biventricular pacing does notcustomize A-RV and A-LV timing independently.

A need remains for methods and systems that provide dynamic AV timingadjustment that adapts to each patient's continually changingcardiovascular status.

SUMMARY

In accordance with embodiments herein, a method for dynamic device basedAV delay adjustment is provided. The method provides electrodes that areconfigured to be located proximate to an atrial (A) site and a rightventricular (RV) site. The method utilizes one or more processors, in animplantable medical device (IMD), for detecting an atrial paced (Ap)event or atrial sensed (As) event. The method determines a measured AVinterval corresponding to an interval between the Ap event or the Asevent and a ventricular sensed event and calculates a percentage-based(PB) offset based on the measured AV interval. The method automaticallydynamically adjusting an AV delay, utilized by the IMD, based on themeasured AV interval and the PB offset and manages a pacing therapy,utilized by the IMD, based on the AV delay after the adjustingoperation.

Optionally, the calculating operation may further comprise setting thePB offset to equal a programmed percentage of the measured AV interval.The adjusting operation may further comprise setting the AV delay tocorrespond to a difference between the measured AV interval and the PBoffset. The calculating and adjusting operations may further comprisesetting the AV delay, in connection with the As event, as AVDs=[(As-Vsinterval)−(PB offset)], wherein the PB offset=(As-Vs interval)*P1%], theAs-Vs interval may correspond to the measured AV interval between the Asevent and a sensed ventricular (Vs) event, and the P1% may correspond toa pre-programmed percentage.

Optionally, the method may provide an electrode that may be configuredto be proximate to a left ventricular (LV) site. The measured AVinterval may comprise a measured A-RV interval and a measured A-LVinterval. The adjusting operation may further comprise adjusting, as theAV delay a delay that may be associated with the As event to a rightsensed ventricular (RVs) event as A-RVDs=[(As-RVs interval)−(PBs-RVoffset)], wherein the PBs-RV offset may represent a first percentagebased offset between the As event and the RVs event and a delay that maybe associated with the As event to a left ventricular sensed (LVs) eventas A-RVDs=[(As-LVs interval)−(PBs-LV offset)], wherein PBs-LV offset mayrepresent a second percentage based offset between the As event and theLVs event.

Optionally, the method may comprise logging a base heart rate associatedwith the measured AV interval. The method may monitor a current heartrate, and may automatically repeat the determining, calculating andadjusting operations when the current heart rate changes by more than apredetermined threshold relative to the base heart rate. The method mayextend the AV delay in proportion to a ratio between the current heartrate and the base heart rate when the current heart rate is slower thanthe base heart rate. The method may extend the AV delay to correspond toa default search AV delay (AVD_(search)). The method may sensing cardiacactivity for a predetermined number of cardiac beats, may identifyingwhether the cardiac activity is indicative of a conduction blockcondition or non-conduction block condition and may repeat thedetermining, calculating and adjusting operations only when thenon-conduction block condition is identified.

Optionally, the identifying operation may comprise identifying thecardiac activity to be indicative of a conduction block condition whenfewer than a select number of cardiac beats exhibit sensed ventricularevents during the default search AV delay AVD_(search). The adjustingmay comprise adjusting a sensed AV delay (AVDs) and a paced AV delay(AVDp). The method may further comprise identifying a presence ofconduction block and, in response thereto, revert the AVDs and base AVDpto AVDs-base and AVDp-base programmed lengths, respectively. The methodmay maintain the base AVDp-base and AVDs-base programmed lengths for aselect second number of cardiac beats.

In accordance with embodiments herein, an implantable medical device(IMD) is provided. The device comprises electrodes that are configuredto be located proximate to an atrial (A) site and a right ventricular(RV) site. Memory stores program instructions. One or more processorsare configured to implement the program instructions to detect an atrialpaced (Ap) event or atrial sensed (As) event, determine a measured AVinterval corresponding to an interval between the Ap event or the Asevent and a ventricular sensed event and calculate a percentage-based(PB) offset based on the measured AV interval. The device automaticallydynamically adjust an AV delay, utilized by the IMD, based on themeasured AV interval and the PB offset and manages a pacing therapy,utilized by the IMD, based on the AV delay after the adjustingoperation.

Optionally, the one or more processors may be configured to set the PBoffset to equal a programmed percentage of the measured AV interval, andmay set the AV delay to correspond to a difference between the measuredAV interval and the PB offset. The one or more processors may beconfigured to perform the calculating and adjusting operations bysetting the AV delay, in connection with the As event, as AVDs=[(As-Vsinterval)−(PB offset)], wherein the PB offset=(As-Vs interval)*P1%], theAs-Vs interval may correspond to the measured AV interval between the Asevent and a sensed ventricular (Vs) event, and the P1% may correspond toa pre-programmed percentage.

The device may comprise an electrode that may be configured to beproximate to a left ventricular (LV) site. The measured AV interval maycomprise a measured A-RV interval and a measured A-LV interval. The oneor more processors may adjust the AV delay by adjusting, as the AVdelay: a delay associated with the As event to a right sensedventricular (RVs) event as A-RVDs=[(As-RVs interval)−(PBs-RV offset)],wherein the PBs-RV offset may represent a first percentage based offsetbetween the As event and the RVs event and a delay associated with theAs event to a left ventricular sensed (LVs) event as A-RVDs=[(As-LVsinterval)−(PBs-LV offset)], wherein PBs-LV offset may represent a secondpercentage based offset between the As event and the LVs event.

Optionally, the one or more processors may be configured to log a baseheart rate associated with the measured AV interval. The one or moreprocessors may be configured to monitor a current heart rate, and mayautomatically repeat the determining, calculating and adjustingoperations when the current heart rate changes by more than apredetermined threshold relative to the base heart rate. The one or moreprocessors may be configured to extend the AV delay in proportion to aratio between the current heart rate and the base heart rate when thecurrent heart rate is slower than the base heart rate. The one or moreprocessors may be configured to: extend the AV delay to correspond to adefault search AV delay (AVD_(search)), may sense cardiac activity for apredetermined number of cardiac beats, may identify whether the cardiacactivity is indicative of a conduction block condition or non-conductionblock condition and may repeat the determining, calculating andadjusting operations only when the non-conduction block condition isidentified.

Optionally, the one or more processors may be configured to perform theidentifying operation by identifying the cardiac activity to beindicative of a conduction block condition when fewer than a selectnumber of cardiac beats exhibit sensed ventricular events during thedefault search AV delay AVD_(search). The one or more processors may beconfigured to adjust a sensed AV delay (AVDs) and a paced AV delay(AVDp), may identify a presence of conduction block and, in responsethereto, revert the AVDs and base AVDp to AVDs-base and AVDp-baseprogrammed lengths, respectively and may maintain the base AVDp-base andAVDs-base programmed lengths for a select second number of cardiacbeats.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an implantable medical device (IMD) intended forsubcutaneous implantation at a site near the heart in accordance withembodiments herein.

FIG. 2 illustrates a schematic view of the IMD in accordance withembodiments herein.

FIG. 3 illustrates a computer implemented method for dynamicdevice-based AV delay adjustment in accordance with embodiments herein.

FIG. 4 illustrates an overall process for implementing the AVsynchronization in accordance with embodiments herein.

FIG. 5 illustrates a process for dynamically adjusting paced and sensedAV delays in accordance with embodiments herein.

FIG. 6 illustrates a process for automatically adjusting sensed andpaced AV delays, in connection with changes in heart rate, in accordancewith embodiments herein.

DETAILED DESCRIPTION

The term “As-Vs interval”, as used herein, refers to a measuredintrinsic conduction time from a sensed atrial (As) event to a sensedventricular (Vs) event. The sensed ventricular event may be a rightventricular event or a left ventricular event. The term “Ap-Vsinterval”, as used herein, refers to a measured intrinsic conductiontime from a paced atrial (Ap) event to a sensed ventricular (Vs) event.The sensed ventricular event may be a right ventricular event or a leftventricular event.

The term “As-RVs interval”, as used herein, refers to a measuredintrinsic conduction time from a sensed atrial (As) event to a sensedright ventricular (RVs) event. The term “Ap-RVs interval”, as usedherein, refers to a measured intrinsic conduction time from a pacedatrial (Ap) event to a sensed right ventricular (RVs) event.

The term “As-LVs interval”, as used herein, refers to a measuredintrinsic conduction time from a sensed atrial (As) event to a sensedleft ventricular (LVs) event. The term “Ap-LVs interval”, as usedherein, refers to a measured intrinsic conduction time from a pacedatrial (Ap) event to a sensed left ventricular (LVs) event.

The term “PBs-RV offset” refers to a percentage-based (PB) offsetcalculated based on a measured As-RVs interval.

The term “PBp-RV offset” refers to a percentage-based offset calculatedbased on a measured Ap-RVs interval.

The term “PBs-LV offset” refers to a percentage-based offset calculatedbased on a measured As-LVs interval.

The term “PBp-RV offset” refers to a percentage-based offset calculatedbased on a measured Ap-LVs interval.

The terms “atrioventricular delay” and “AVD” refer to a programmed timedelay to be used by the implantable medical device in connection withdelivering therapy.

The term “AVDs” refer to an AVD in connection with delivering therapy ata ventricular site following a sensed atrial event, when an intrinsicventricular event does not occur before AVD expires.

The term “AVDp” is used to refer to an AVD in connection with deliveringtherapy at a ventricular site following a paced atrial event, when anintrinsic ventricular event does not occur before AVD expires.

The term “LV only pacing” refers to a mode of operation for an implantedmedical device in which the LV is paced but the RV is not paced.

In accordance with embodiments herein, methods and systems are describedfor dynamic adjustment of AVD while accounting for a dependence of theintrinsic AV conduction interval on heart rate. Embodiments hereincalculate an offset as a percentage of a real-time measured AV interval,and dynamically adjust the AVD by subtracting the percentage offset fromthe measured AV interval. Additionally or alternatively, embodiments mayapply a percent-based offset to the RV and LV leads independently, basedon the respective AV interval measurements. Thus, biventricular pacingmay be delivered in terms of two AVD values (A-RV delay and A-LV delay),rather than based on one AVD and a programmed interventricular delay(VVD), which traditionally determines the timing of LV-pacing relativeto RV-pacing.

Embodiments herein subtract a dynamic PB offset from the measured AVinterval, where the dynamic PB offset is a programmed percentage of themeasured AV interval (e.g., 20%). By dynamically programming the AVD tothe intrinsic AV interval reduced by a percentage of the intrinsic AVinterval, embodiments herein maintain fusion between (a) the intrinsicwavefront conducting down the septum and (b) the RV- and LV-paced beats,over a broad range of heart rates. Further, embodiments herein achieve a“triple-fusion” of all 3 wavefronts (e.g., intrinsic A-V conduction,RV-paced beat, and LV-paced beat). In addition, embodiments hereinafford the ability to independently program A-RV and A-LV delays in thesame manner. In other words, the A-RV and A-LV delays may each have aseparate offset that is determined relative to the A-RVs and A-LVsintervals, respectively (e.g., 20% of A-RV interval and 40% of A-LVinterval). The new AVD values are programmed to be shorter than themeasured AV interval's in connection with paced and/or sensed atrialevents. The percentage offset may be programmable to allow forpatient-specific optimization (e.g., 5-50% in increments of 5%, with adefault value of 20%).

In accordance with embodiments herein, the percent-based offsets can beexpanded to apply independently to the RV and LV leads, based on therespective AV interval measurements. Specifically, the As-RVs interval(during A-sensing) or the Ap-RVs interval (during A-pacing) aremeasured, and the A-RV delay is dynamically programmed by subtracting apercentage of the Ap-RVs or As-RVs interval (e.g., 20%), while aparallel programming of the A-LV delay occurs in the same manner. Ingeneral, the PB offset used for the A-LV delay should be larger (e.g.,40%) than for the A-RV delay, as the LV-paced wavefront must travelfurther to simultaneously collide with the intrinsic AV conduction andRV-paced wavefront. These two independent AVD values may be calculatedbased on the respective AV intervals corresponding to the two pacingvectors used (e.g., A-RV and A-LVD1), both of which can be measuredduring the same cardiac beat.

FIG. 1 illustrates an implantable medical device (IMD) 100 intended forsubcutaneous implantation at a site near the heart 111, in accordancewith embodiments herein. The IMD 100 may be a dual-chamber stimulationdevice, capable of treating both fast and slow arrhythmias withstimulation therapy, including cardioversion, pacing stimulation, animplantable cardioverter defibrillator, suspend tachycardia detection,tachyarrhythmia therapy, and/or the like. The IMD 100 may include ahousing 101 to hold the electronic/computing components. The housing 101(which is often referred to as the “can,” “case,” “encasing,” or “caseelectrode”) may be programmably selected to act as the return electrodefor certain stimulus modes. The housing 101 further includes a connector109 with a plurality of terminals 200-210 (shown in FIG. 2).

The IMD 100 is shown in electrical connection with a heart 111 by way ofa left atrial (LA) lead 120 having a right lead 112 and a left atrial(LA) ring electrode 128. The IMD 100 is also in electrical connectionwith the heart 111 by way of a right ventricular (RV) lead 110 having,in this embodiment, a left ventricle (LV) electrode 132 (e.g., P4), anLV electrode 134 (e.g., M3), an LV electrode 136 (e.g., M2), and an LVelectrode 138 (e.g., D1). The RV lead 110 is transvenously inserted intothe heart 111 to place the RV coil 122 in the RV apex, and the SVC coilelectrode 116. Accordingly, the RV lead 110 is capable of receivingcardiac signals and delivering stimulation in the form of pacing andshock therapy to the right ventricle 140 (also referred to as the RVchamber). The IMD 100 includes RV tip electrode 126, and a right atrium(RA) electrode 123. The RV lead 110 includes an RV tip electrode 126, anRV ring electrode 124, an RV coil electrode 122, and an SVC coilelectrode 116.

The IMD 100 includes a left ventricle 142 (e.g., left chamber) pacingtherapy, and is coupled to a multi-pole LV lead 114 designed forplacement in various locations such as a “CS region” (e.g., venousvasculature of the left ventricle, including any portion of the coronarysinus (CS), great cardiac vein, left marginal vein, left posteriorventricular vein, middle cardiac vein, and/or small cardiac vein or anyother cardiac vein accessible by the coronary sinus), the epicardialspace, and/or the like.

In an embodiment, the LV lead 114 is designed to receive atrial andventricular cardiac signals and to deliver left ventricular pacingtherapy using a set of multiple LV electrodes 132, 134, 136, 138. The LVlead 114 also may deliver left atrial pacing therapy using at least anLA ring electrode 128 and shocking therapy using at least the LA ringelectrode 128. In alternate embodiments, the LV lead 114 includes the LVelectrodes 138, 136, 134, and 132, but does not include the LA electrode130. The LV lead 114 may be, for example, the Quartet™ LV pacing leaddeveloped by St. Jude Medical Inc. (headquartered in St. Paul, Minn.),which includes four pacing electrodes on the LV lead. Although threeleads 110, 112, and 114 are shown in FIG. 1, fewer or additional leadswith various configurations of pacing, sensing, and/or shockingelectrodes may optionally be used. For example, the LV lead 114 may havemore or less than four LV electrodes 132-138.

The LV electrode 132 (also referred to as P4) is shown as being the most“distal” LV electrode with reference to how far the electrode is fromthe right ventricle 140. The LV electrode 138 (also referred to as D1)is shown as being the most “proximal” LV electrode 132-138 to the leftventricle 142. The LV electrodes 136 and 134 are shown as being “middle”LV electrodes (also referred to as M3 and M2), between the distal andproximal LV electrodes 138 and 132, respectively. Accordingly, so as tomore aptly describe their relative locations, the LV electrodes 138,136, 134, and 132 may be referred to respectively as electrodes D1, M2,M3, and P4 (where “D” stands for “distal”, “M” stands for “middle”, and“P” stands from “proximal”, and the s are arranged from most distal tomost proximal, as shown in FIG. 1). Optionally, more or fewer LVelectrodes may be provided on the lead 114 than the four LV electrodesD1, M2, M3, and P4.

The LV electrodes 132-138 are configured such that each electrode may beutilized to deliver pacing pulses and/or sense pacing pulses (e.g.,monitor the response of the LV tissue to a pacing pulse). In a pacingvector or a sensing vector, each LV electrode 132-138 may be controlledto function as a cathode (negative electrode). Pacing pulses may bedirectionally provided between electrodes to define a pacing vector. Ina pacing vector, a generated pulse is applied to the surroundingmyocardial tissue through the cathode. The electrodes that define thepacing vectors may be electrodes in the heart 111 or located externallyto the heart 111 (e.g., on a housing/case device 101). For example, thehousing/case 101 may be referred to as the housing 101 and function asan anode in unipolar pacing and/or sensing vectors. The RV coil 122 mayalso function as an anode in unipolar pacing and/or sensing vectors. TheLV electrodes 132-138 may be used to provide various different vectors.Some of the vectors are intraventricular LV vectors (e.g., vectorsbetween two of the LV electrodes 132-138), while other vectors areinterventricular vectors (e.g., vectors between an LV electrode 132-138and the RV coil 122 or another electrode remote from the left ventricle142). Various exemplary bipolar sensing vectors with LV cathodes thatmay be used for sensing using the LV electrodes D1, M2, M3, and P4 andthe RV coil 122. Various other types of leads and the IMD 100 may beused with various other types of electrodes and combinations ofelectrodes. Utilizing an RV coil electrode as an anode is merely oneexample. Various other electrodes may be configured as the anodeelectrode.

FIG. 2 illustrates a schematic view of the IMD 100. The IMD 100 may be adual-chamber stimulation device, capable of treating both fast and slowarrhythmias with stimulation therapy, including cardioversion, pacingstimulation, an implantable cardioverter defibrillator, suspendtachycardia detection, tachyarrhythmia therapy, and/or the like.

The IMD 100 has a housing 101 to hold the electronic/computingcomponents. The housing 101 (which is often referred to as the “can,”“case,” “encasing,” or new to me makes “case electrode”) may beprogrammably selected to act as the return electrode for certainstimulus modes. The housing 101 further includes a connector (not shown)with a plurality of terminals 200-210. The terminals may be connected toelectrodes that are located in various locations within and around theheart. For example, the terminals may include: a terminal 200 to becoupled to a first electrode (e.g., a tip electrode) located in a firstchamber; a terminal 202 to be coupled to a second electrode located in asecond chamber; a terminal 204 to be coupled to an electrode located inthe first chamber; a terminal 206 to be coupled to an electrode locatedin the second chamber; an a terminal 208 to be coupled to an electrode;and a terminal 210 to be coupled to an electrode located in the shockingcircuit 280. The type and location of each electrode may vary. Forexample, the electrodes may include various combinations of a ring, atip, a coil and shocking electrodes and the like.

The IMD 100 includes a programmable microcontroller 220 that controlsvarious operations of the IMD 100, including cardiac monitoring andstimulation therapy. The microcontroller 220 includes a microprocessor(or equivalent control circuitry), one or more processors, RAM and/orROM memory, logic and timing circuitry, state machine circuitry, and I/Ocircuitry. The IMD 100 further includes an atrial and/or ventricularpulse generator 222 that generates stimulation pulses for connecting thedesired electrodes to the appropriate I/O circuits, thereby facilitatingelectrode programmability. The switch 226 is controlled by a controlsignal 228 from the microcontroller 220.

A pulse generator 222 is illustrated in FIG. 2. Optionally, the IMD 100may include multiple pulse generators, similar to the pulse generator222, where each pulse generator is coupled to one or more electrodes andcontrolled by the microcontroller 220 to deliver select stimuluspulse(s) to the corresponding one or more electrodes. The IMD 100includes sensing circuits 244 selectively coupled to one or moreelectrodes that perform sensing operations, through the switch 226 todetect the presence of cardiac activity in the chamber of the heart 111.The output of the sensing circuits 244 is connected to themicrocontroller 220 which, in turn, triggers, or inhibits the pulsegenerator 222 in response to the absence or presence of cardiacactivity. The sensing circuits 244 receives a control signal 246 fromthe microcontroller 220 for purposes of controlling the gain, threshold,polarization charge removal circuitry (not shown), and the timing of anyblocking circuitry (not shown) coupled to the inputs of the sensingcircuits.

In the example of FIG. 2, the sensing circuit 244 is illustrated.Optionally, the IMD 100 may include multiple sensing circuits 244,similar to the sensing circuit 244, where each sensing circuit iscoupled to one or more electrodes and controlled by the microcontroller220 to sense electrical activity detected at the corresponding one ormore electrodes. The sensing circuit 224 may operate in a unipolarsensing configuration or a bipolar sensing configuration.

The IMD 100 further includes an analog-to-digital (A/D) data acquisitionsystem (DAS) 250 coupled to one or more electrodes via the switch 226 tosample cardiac signals across any pair of desired electrodes. The DAS250 is configured to acquire intracardiac electrogram signals, convertthe raw analog data into digital data and store the digital data forlater processing and/or telemetric transmission to an external device254 (e.g., a programmer, local transceiver, or a diagnostic systemanalyzer). The DAS 250 is controlled by a control signal 256 from themicrocontroller 220.

The microcontroller 220 includes an arrhythmia detector 234 foranalyzing cardiac activity signals sensed by the sensing circuit 244and/or the DAS 250. The arrhythmia detector 234 is configured to analyzecardiac signals sensed at various sensing sites.

The microcontroller 220 further includes an AVD adjustment module 235that is configured to perform, among other things, the operations of themethods described herein. The AVD adjustment module 235 detects anatrial paced (Ap) event or atrial sensed (As) event; determines ameasured AV interval corresponding to an interval between the Ap eventor the As event and a ventricular sensed event; calculates apercentage-based (PB) offset based on the measured AV interval; andautomatically dynamically adjusts an AV delay, utilized by the IMD,based on the measured AV interval and the PB offset. The AVD adjustmentmodule 235 manages a pacing therapy, utilized by the IMD, based on theAV delay after the adjusting operation.

The AVD adjustment module 235 is further configured to set the PB offsetto equal a programmed percentage of the measured AV interval, and setthe AV delay to correspond to a difference between the measured AVinterval and the PB offset. The AVD adjustment module 235 is furtherconfigured to perform the calculating and adjusting operations bysetting the AV delay, in connection with the As event, as AVDs=[(As-Vsinterval)−(PB offset)], wherein the PB offset=(As-Vs interval)*P1%], theAs-Vs interval corresponds to the measured AV interval between the Asevent and a sensed ventricular (Vs) event, and the P1% corresponds to apre-programmed percentage.

In connection with some embodiments, an electrode is provided proximateto a left ventricular (LV) site. The AVD adjustment module 235 isfurther configured to determine the measured AV interval by determininga measured A-RV interval and a measured A-LV interval. The AVDadjustment module 235 is further to adjust the AV delay by adjusting, asthe AV delay: a delay associated with the As event to a right sensedventricular (RVs) event as A-RVDs=[(As-RVs interval)−(PBs-RV offset)],wherein the PBs-RV offset represents a first percentage based offsetbetween the As event and the RVs event; and a delay associated with theAs event to a left ventricular sensed (LVs) event as A-RVDs=[(As-LVsinterval)−(PBs-LV offset)], wherein PBs-LV offset represents a secondpercentage based offset between the As event and the LVs event. The AVDadjustment module 235 is further configured to log a base heart rateassociated with the measured AV interval. The AVD adjustment module 235is further configured to monitor a current heart rate, and automaticallyrepeat the determining, calculating and adjusting operations when thecurrent heart rate changes by more than a predetermined thresholdrelative to the base heart rate. The AVD adjustment module 235 isfurther configured to extend the AV delay in proportion to a ratiobetween the current heart rate and the base heart rate when the currentheart rate is slower than the base heart rate.

The AVD adjustment module 235 is further configured to: extend the AVdelay to correspond to a default search AV delay (AVD_(search)); sensingcardiac activity for a predetermined number of cardiac beats; identifywhether the cardiac activity is indicative of a conduction blockcondition or non-conduction block condition; and repeat the determining,calculating and adjusting operations only when the non-conduction blockcondition is identified. The AVD adjustment module 235 is furtherconfigured to perform the identifying operation by identifying thecardiac activity to be indicative of a conduction block condition whenfewer than a select number of cardiac beats exhibit sensed ventricularevents during the default search AV delay AVD_(search). The AVDadjustment module 235 is further configured to adjust a sensed AV delay(AVDs) and a paced AV delay (AVDp), identify a presence of conductionblock and, in response thereto, revert the AVDs and base AVDp toAVDs-base and AVDp-base programmed lengths, respectively; and maintainthe base AVDp-base and AVDs-base programmed lengths for a select secondnumber of cardiac beats.

The microcontroller 220 is operably coupled to a memory 260 by asuitable data/address bus 262. The programmable operating parametersused by the microcontroller 220 are stored in the memory 260 and used tocustomize the operation of the IMD 100 to suit the needs of a particularpatient. The operating parameters of the IMD 100 may be non-invasivelyprogrammed into the memory 260 through a telemetry circuit 264 intelemetric communication via communication link 266 (e.g., MICS,Bluetooth low energy, and/or the like) with the external device 254.

The IMD 100 can further include one or more physiological sensors 270.Such sensors are commonly referred to as “rate-responsive” sensorsbecause they are typically used to adjust pacing stimulation ratesaccording to the exercise state of the patient. However, thephysiological sensor 270 may further be used to detect changes incardiac output, changes in the physiological condition of the heart, ordiurnal changes in activity (e.g., detecting sleep and wake states).Signals generated by the physiological sensors 270 are passed to themicrocontroller 220 for analysis. While shown as being included withinthe IMD 100, the physiological sensor(s) 270 may be external to the IMD100, yet still, be implanted within or carried by the patient. Examplesof physiological sensors might include sensors that, for example, senserespiration rate, pH of blood, ventricular gradient, activity,position/posture, minute ventilation (MV), and/or the like.

A battery 272 provides operating power to all of the components in theIMD 100. The battery 272 is capable of operating at low current drainsfor long periods of time, and is capable of providing a high-currentpulses (for capacitor charging) when the patient requires a shock pulse(e.g., in excess of 2 A, at voltages above 2 V, for periods of 10seconds or more). The battery 272 also desirably has a predictabledischarge characteristic so that elective replacement time can bedetected. As one example, the IMD 100 employs lithium/silver vanadiumoxide batteries.

The IMD 100 further includes an impedance measuring circuit 274, whichcan be used for many things, including sensing respiration phase. Theimpedance measuring circuit 274 is coupled to the switch 226 so that anydesired electrode and/or terminal may be used to measure impedance inconnection with monitoring respiration phase.

The microcontroller 220 further controls a shocking circuit 280 by wayof a control signal 282. The shocking circuit 280 generates shockingpulses of low (e.g., up to 0.5 joules), moderate (e.g., 0.5-10 joules),or high energy (e.g., 11 to 40 joules), as controlled by themicrocontroller 220. Such shocking pulses are applied to the patient'sheart through shocking electrodes. Maybe noted that the shock therapycircuitry is optional and may not be implemented in the IMD 100.

The microcontroller 220 further includes timing control 232 used tocontrol the timing of such stimulation pulses (e.g., pacing rate,atria-ventricular (AV) delay, atrial interconduction (A-A) delay, orventricular interconduction (V-V) delay, etc.) as well as to keep trackof the timing of refractory periods, blanking intervals, noise detectionwindows, evoked response windows, alert intervals, marker channeltiming, and the like. The switch 226 includes a plurality of switchesfor connecting the desired electrodes to the appropriate I/O circuits,thereby providing complete electrode programmability. Accordingly, theswitch 226, in response to a control signal 228 from the microcontroller220, determines the polarity of the stimulation pulses (e.g., unipolar,bipolar, etc.) by selectively closing the appropriate combination ofswitches (not shown) as is known in the art.

The microcontroller 220 is illustrated to include timing control 232 tocontrol the timing of the stimulation pulses (e.g., pacing rate,atrioventricular (AV) delay, atrial interconduction (A-A) delay, orventricular interconduction (V-V) delay, etc.). The AV delay is managedto provide a fusion AV delay to fuse timing of pacing pulses withintrinsic wave fronts. The timing control 232 may also be used for thetiming of refractory periods, blanking intervals, noise detectionwindows, evoked response windows, alert intervals, marker channeltiming, and so on. Microcontroller 220 also has a morphology detector236 to review and analyze one or more features of the morphology ofcardiac signals. Although not shown, the microcontroller 220 may furtherinclude other dedicated circuitry and/or firmware/software componentsthat assist in monitoring various conditions of the patient's heart andmanaging pacing therapies.

The IMD 100 is further equipped with a communication modem(modulator/demodulator) 240 to enable wireless communication with otherdevices, implanted devices and/or external devices. In oneimplementation, the communication modem 240 may use high-frequencymodulation of a signal transmitted between a pair of electrodes. As oneexample, the signals may be transmitted in a high-frequency range ofapproximately 10-80 kHz, as such signals travel through the body tissueand fluids without stimulating the heart or being felt by the patient.

FIG. 3 illustrates a computer implemented method for dynamicdevice-based AV delay adjustment in accordance with embodiments herein.The method is under control of one or more processors configured withspecific executable instructions. As explained hereafter, the operationsof FIG. 3 may be performed during a search mode in connection with adesired one or more cardiac beats measured during the search mode.Optionally, the operations of FIG. 3 may be performed followingtermination of the search mode after an identification of whether apatient is experiencing normal conduction or an abnormal conductionblock condition.

Optionally, the operations of FIG. 3 may be performed when the heartrate changes, relative to a base heart rate, by more than a thresholdlevel.

At 302, the one or more processors detect a paced atrial (Ap) event orsensed atrial (As) event. When the paced or sensed atrial event isdetected, one or more AV timers are started.

At 304, the one or more processors monitor for a sensed ventricular (Vs)event. The Vs event may occur at an RV sensing site or an LV sensingsite. Optionally, an RV sensed (RVs) event may be detected separate froma sensed LV (LVs)(LBS) event that is detected.

At 306, the one or more processors determine a measured AV interval. Themeasured AV interval may correspond to an interval between a sensedatrial event and a sensed ventricular event (As-Vs interval) and/or aninterval between a paced atrial event and a sensed ventricular event(Ap-Vs interval).

At 307, the one or more processors calculate a percentage based (PB)offset that is derived from the measured AV interval. For example, thePB offset may be set to equal a percentage (e.g., 20%) of the measuredAV interval, such as PB offset=(AV interval)*P1%, where P1% correspondsto a percentage that is programmed by a clinician and/or automaticallyderived by the IMD based on recorded physiologic characteristics.Additionally or alternatively, when separate As-Vs and Ap-Vs intervalsare measured, the PB offset may be based solely on the As-Vs interval(e.g., PB offset=(AV interval)*P1%). Additionally or alternatively, anatrial sense related PB offset and atrial pace related PB offset may becalculated based on the As-Vs and/or Ap-Vs intervals, respectively. Forexample, an atrial pace related PB offset may be calculated as aprogrammed percentage (e.g., 25%) of the Ap-Vs interval, while an atrialsense related PB offset may be calculated as a program percentage (e.g.,20%) of the As-Vs interval. As a further example, the atrial senserelated PB offset may be set as: PBs offset=(As-Vs interval)*P1%, whereP1% corresponds to a percentage that is programmed by a clinician and/orautomatically derived by the IMD based on recorded physiologiccharacteristics. The atrial pace related PB offset may be set as: PBpoffset=(Ap-Vs interval)*P2%, where P2% corresponds to a percentage thatis programmed by a clinician and/or automatically derived by the IMDbased on recorded physiologic characteristics.

At 308, the one or more processors automatically and dynamically adjustone or more AV delays based on the measured AV interval and the PBoffset(s). For example, the one or more processors may set an AV delayassociated with sensed atrial events as AVDs=[(As-Vs interval)−(PBsoffset)], where the PBs offset is calculated based on the percentage P1%of the As-Vs interval. As another example, the one or more processorsmay set an AV delay associated with a paced atrial event as AVDp=[(Ap-Vsinterval)−(PBp offset)], where the PBp offset is calculated based on thepercentage (P2%) of the Ap-Vs interval.

Additionally or alternatively, each time the methods and systems hereinreset/reprogram the AVDs and AVDp values, the current heart rate islogged rate. Accordingly, an optional operation may be provided at 310,in which the one or more processors record the current heart rate as a“base” or “logged” heart rate corresponding to the measured AV intervalthat is utilized to set the AVDs and AVDp values. As explained below inconnection with FIG. 6, an automatic rate-responsive AVDs and AVDpadjustment may be performed when the heart rate reduces. As that heartrate slows down, the AVDs and AVDp values are automatically extended,such as in a linear fashion, until the next time that the AV interval ismeasured (e.g., up to 256 beats later).

The IMD manages a pacing therapy utilizing various AV delays that arechanged over the course of operation based on various criteria, such asparticular physiologic behavior exhibited by the heart, completion ofpredetermined numbers of cardiac beats, and the like.

FIG. 4 illustrates an overall process for implementing the AVsynchronization in accordance with embodiments herein. The AVsynchronization process utilizes the dynamic device-based AV delayadjustment process of FIG. 3 (and/or FIG. 5).

At 402, when the AV synchronization process is activated, the one ormore processors enter a search mode, in which the processors set theAVDp and AVDs values to equal corresponding AV search delays(collectively referred to as AVD_(search)). The AV search delays are setto be sufficiently long to wait for an intrinsic RV event that may bedelayed following a paced atrial or sensed atrial event. However, the AVsearch delays, AVD_(search), are not too long in order to avoid delayingpacing when a patient should otherwise be paced. For example, theAVD_(search) may be set to between 300 and 400 ms, and more preferablythe AVDp may be set to equal 300 ms to 350 ms, while the AVDs may be setto equal 325 ms to 375 ms. Additionally or alternatively, oneAVD_(search) may be set in connection with measuring an As-Vs interval(e.g., 325 ms), while a second AVD_(search) may be set in connectionwith measuring an Ap-Vs interval (e.g., 350 ms). The processors mayremain in the search mode for a predetermined number of beats (e.g., 5beats, 10 beats) and/or a predetermined period of time (e.g., 10second). Additionally or alternatively, the processors may remain in thesearch mode until a condition is satisfied, such as detecting aparticular physiologic pattern (e.g., detecting 3 consecutive Vsevents). While in the search more, the processors track the cardiacactivity.

When the search mode is terminated, the one or more processors determinewhether the tracked cardiac activity is indicative of conduction blockor whether a sufficient number of Vs events were detected. For example,when all or a select number of the beats, during the search mode,exhibit Vs events that are detected before the AVD_(search) timeexpires, the processors may declare the series of beats to exhibit anormal or non-blocked condition, in response to which flow moves to 404.As a further example, during a series of 4-8 beats, 3 or moreconsecutive beats may exhibit sensed ventricular Vs events before theAVD_(search) time expires, in which case the processors declare theseries of events to be normal.

When flow advances to 404, the one or more processors measure one ormore AV intervals and set the AVD based on the measured AV interval asdescribed herein (e.g., in connection with the operations of FIGS. 3and/or 5). The As-Vs interval and Ap-Vs interval used to define the AVDsand AVDp values may be determined from a select end or intermediate oneof the beats measured during the search mode, such as the third orfourth event/beat in order to allow for the AV interval to stabilizefollowing the change to the AVD_(search) time. Optionally, the As-Vsinterval and Ap-Vs interval may be calculated as an average (or othermathematical combination) of multiple As-Vs intervals and Ap-Vsintervals, respectively, for a desired number of multiple beats.Optionally, the AVDs and AVDp may be set at 404 in various manners,based upon the nature of the events that occur during the search mode.For example, both of the AVDs and AVDp values may be set, as noted abovein connection with FIG. 3, in response to a select number (e.g.,three-five) consecutive Vs events occurring during the search mode (at402).

Additionally or alternatively, the AVDs and AVDp delays may be set inalternative manners in response to other combinations of atrial andventricular events occurring during the search mode. It may be desirableto utilize select combinations of atrial and ventricular events as acriteria for setting the AVDs and AVDp delays, such as in order to skipsingle or paired ectopic premature ventricular contractions (PVCs). Forexample, the one or more processors may search for a particular type ofatrial event during a select beat within the search mode. For example,the one or more processors may determine the type of atrial event thatoccurs during the third, fourth or fifth beat during the search mode,and based thereon, set the AVDs and AVDp delays in a desired manner. Asa more specific example, when the processors determine that a sensedatrial As event occurs during the third beat, but before the thirdsensed ventricular event, the processors may set the AV delays asfollows: AVDs=(As-Vs interval)−(PBs offset) and AVDp=(As-Vsinterval)−PBs offset)*R, where R may be a ratio between the measuredAp-Vs interval and As-Vs interval (e.g., R=(Ap-Vs)/(As-Vs)). In theforegoing example, both of the AVDs and AVDp are set based on the As-Vsinterval and PBs offset. When either of the Ap-Vs interval or As-Vsinterval cannot be measured, the value for R may be a preprogrammedratio (e.g., 1.3-1.5). As another specific example, alternatively, whenthe processors determine that a paced atrial Ap event occurs before thethird sensed ventricular event, the processors may set the AV delaysbased on the Ap-Vs interval and PBp offset as follows: AVDp=(Ap-Vsinterval)−(PBp offset) and AVDp=(Ap-Vs interval)−(PBp offset)/R. Bysetting the AVDs and AVDp based on the type of atrial event thatoccurred during the third or a later beat, the processors skip single orpaired ectopic PVC beats.

The AVDp and AVDs values set at 404 are maintained for a select firstnumber of cardiac beats (e.g., 20-40 beats) associated with a normal ornon-conduction block condition.

Returning to 402, when fewer than the select number of the beats exhibitVs events during the AVD_(search), the processors may declare the seriesof beats to exhibit an abnormal or conduction block condition. When anabnormal or conduction block condition is identified, flow moves to 406.For example, during the search mode, three consecutive Vs events do notoccur. Alternatively, during the series of 4-8 beats, fewer than 3consecutive beats may exhibit Vs events before the AVD_(search) timeexpires.

At 406, the processors identify the presence of conduction block (or asimilar abnormal condition), and in response thereto, revert the AVDsand AVDp delays to base programmed lengths (e.g., set AVDp_(-base) equalto 100 ms to 150 ms and set AVD_(s-base) equal to 125 ms to 175 ms). Thebase AVDp-base and AVDs-base lengths are maintained for a select secondnumber of cardiac beats (e.g., 200-300 beats).

The AVDp and AVDs values set at 404 or 406 are utilized by the IMD forcorresponding numbers of cardiac beats (e.g., 20-40 or 200-300), andthereafter flow continues to 410. At 410, after the corresponding numberof select cardiac beats, the one or more processors reset the AVDp andAVDs values to the AV search delay AVD_(search), thereby reentering asearch mode. The AV search delays set at 410 may be the same as ordiffer from the AV search delays set at 402. The duration of the searchmode at 410 may be the same as or different from the duration of thesearch mode at 402. For example, the processors may maintain the searchmode at 410 for 5 or more beats with the AVDp=350 ms and AVDs=325 ms. At410, the one or more processors determine whether a select number ofconsecutive sensed ventricular Vs events occur and based thereon, flowbranches along 412 or 414. For example, when three or another number ofconsecutive Va events are detected during the search mode, flow branchesalong 414.

At 414, the one or more processors measure one or more AV intervals andset the AVDp and AVDs based on the measured AV intervals and PB offsets.As explained above in connection with 404, at 416, the As-Vs intervaland Ap-Vs interval, used to define the AVDs and AVDp values, may bedetermined from a select one of the beats measured during the searchmode or calculated as an average (or other mathematical combination) ofmultiple As-Vs intervals and Ap-Vs intervals.

Optionally, the AVDs and AVDp may be set at 416 in other manners, basedupon the nature of the events that occurred during the search mode (asdescribed above in connection with 404). For example, when theprocessors determine that a sensed atrial As event occurs during thethird beat, but before the third sensed ventricular event, theprocessors may set the AV delays as follows: AVDs=[(As-Vsinterval)−(As-Vs interval)*P1%] and AVDp=[(As-Vs interval)−(As-Vsinterval)*P1%*R]. Alternatively, when the processors determine that apaced atrial Ap event occurs before the third sensed ventricular event,the processors may set the AV delays as follows: AVDs=[(Ap-Vsinterval)−(Ap-Vs interval)*P3%] and AVDp=[(Ap-Vs interval)−(Ap-Vsinterval)*P3%/R]. Thereafter, the AVDp and AVDs values set at 416 aremaintained for a select number of cardiac beats (e.g., 200-300 beats).

Returning to 410, when the one or more processors determine that fewerthan the select number of consecutive sensed ventricular Vs eventsoccur, the processors determined that the patient exhibited a conductionblock condition and in response thereto, flow branches along 412 andreturns to 406. For example, the processors may identify a conductionblock condition when the processors do not detect three or anotherselect number of consecutive sensed ventricular Vs events during thesearch mode, and flow branches along 412. As noted above, at 406, theAVDp and AVDs values revert to the base programmed lengths for a longerselect number of beats, such as 300×2^(N) beats before reentering thesearch mode again. The variable N equals the number of consecutivesearches in which conduction block was identified.

Additionally or alternatively, anytime the select number of consecutivesensed ventricular Vs events occur while the AVDp and AVDs values arealready reduced (e.g., within either a 30- or 300-beat window), bothAVDp and AVDs values are further reduced, as described above, such asfor another 30 beats before re-entering the search mode. Additionally oralternatively, whenever the processors determine that it is desirable tofurther reduce the AVDp and AVDs values, after already being reduced,the processors may first enter the search mode for a shortened searchwindow (e.g., after 30 beats instead of 300 beats) to allow theprocessors to perform a fast AV interval assessment.

The foregoing process of FIG. 3 for dynamically adjusting paced andsensed AV delays is described in connection with one example of anoverall synchronization process (FIG. 4). Optionally, the dynamicprocess of FIG. 3 may be implemented in connection with other static ordynamic methods for programming paced and sensed AV delays.

FIG. 5 illustrates a process for dynamically adjusting paced and sensedAV delays in accordance with an alternative embodiment. In the exampleof FIG. 5, the process of FIG. 3 for utilizing a percentage based offsetis expanded to apply independently to an RV pacing site and one or moreLV pacing sites, such as when RV and LV leads are separately implanted.As explained hereafter, a first AVDs and first AVDp are calculated inconnection with an RV sensing/pacing site, and a second AVDs and secondAVDp are calculated in connection with an LV sensing/pacing site. Theoperations of FIG. 5 may be performed during one or more of the searchmodes (described in connection with FIG. 4) in connection with a desiredone or more cardiac beats measured during the search mode. Optionally,the operations of FIG. 5 may be performed following termination of thesearch mode after an identification of whether a patient is experiencingnormal conduction or an abnormal conduction block condition.

At 502, the one or more processors detect a paced atrial Ap event orsensed atrial As event. When the paced or sensed atrial event isdetected, an A-LV timer is started and an A-RV timer is started.

At 504, the one or more processors monitor for and detect a right sensedventricular RVs event, and monitor for and detect a left sensedventricular LVs event. The RVs event occurs at an RV sensing site andthe LVs event occurs at an LV sensing site. When the LV lead includesmultiple electrodes, such as in connection with multipoint pacing (MPP),various ones of the LV electrodes may be designated to be utilized asthe LV sensing site. By way of example, the distal or one of theintermediate LV sensing sites may be utilized to monitor for and detectleft sensed ventricular events.

At 506, the one or more processors determine a measured A-RV intervaland a measured A-LV interval. The measured A-RV interval may correspondto an interval between a sensed atrial event and a sensed rightventricular event (As-RVs interval) and/or an interval between a pacedatrial event and a right sensed ventricular event (AP-RVs interval). Themeasured A-LV interval may correspond to an interval between a sensedatrial event and a sensed left ventricular event (As-LVs interval)and/or an interval between a paced atrial event and a sensed leftventricular event (Ap-LVs interval).

At 507, the one or more processors calculate a percentage based (PB)offset based on the measured AV interval. For example, the PB offset maybe set to equal a programmed percentage (e.g., 20%) of the measured AVinterval, such as PB offset=(AV interval)*P1%, where P1% corresponds toa percentage that is programmed by a clinician and/or automaticallyderived by the IMD based on recorded physiologic characteristics.Additionally or alternatively, when separate As-Vs and Ap-Vs intervalsare measured, the PB offset may be based solely on the As-Vs interval(e.g., PB offset=(As-Vs interval)*P1%).

Additionally or alternatively, as explained above in connection withFIG. 3, an atrial sense related PB offset and atrial pace related PBoffset may be calculated separately on the As-Vs and/or Ap-Vs intervals,respectively. Further, separate PB offsets may be calculated inconnection with the LV sensing/pacing site(s). For example, an atrialpacerelated PB offset may be calculated as a programmed percentage(e.g., 25%) of the Ap-LVs interval, while an atrial sense related PBoffset may be calculated as a program percentage (e.g., 20%) of theAs-LVs interval. As a further example, separate PB offsets may becalculated in connection with each sensed atrial and paced atrial eventrelative to each RV sensing/pacing site and relative to each LVsensing/pacing site (e.g., PBs-RV offset, PBp-RV offset, PBs-LV offset,PBp-LV offset). The programmed percentage that is used to calculate theoffsets associated with the RV may differ from the programmed percentagethat is used to calculate the offsets associated with the LV.

At 508, the one or more processors automatically and dynamically adjustsone or more A-RV delays and one or more A-LV delays. For example, theone or more processors may set a delay associated with a sensed atrialevent to sensed right ventricular event as A-RVDs=[(As-RVsinterval)−(PBs-RV offset)]. As another example, the one or moreprocessors may set a delay associated with a paced atrial event tosensed right ventricular event as A-RVDp=[(Ap-RVs interval)−(PBp-RVoffset). Similarly, the one or more processors set the delays associatedwith sensed atrial/paced events to sensed left ventricular events asA-LVDs=[(As-LVs interval)−(PBs-LV offset)] and A-LVDp=[(As-LVpinterval)−(PBp-RV offset)].

An optional operation may be provided at 510, in which the one or moreprocessors record the current heart rate as a “base” or “logged” heartrate corresponding to the measured AV interval that is utilized to setthe AVDs and AVDp values. As explained below in connection with FIG. 6,an automatic rate-responsive AVDs and AVDp adjustment may be performedwhen the heart rate changes.

The operations of FIG. 5 are described in connection with a single RVpacing/sensing site and a single LV pacing/sensing site. Optionally, theproposed independent A-RV and A-LV delays, may be expanded for use withmultiple LV pacing/sensing sites. With biventricular MPP, AVDs and AVDpvalues for three or more pacing sites may be dynamically programmed:A-RVDs and A-RVDp, A-LVDs1 and A-LVDp1, and A-LVDs2 and A-LVDp2.Optionally, with LV-only MPP, only two AVD values would be dynamicallyprogrammed: A-LVDs1 and A-LVDp1, and A-LVDs2 and A-LVDp2 such as for anintermediate and distal electrodes.

FIG. 6 illustrates a process for automatically adjusting sensed andpaced AV delays, in connection with changes in heart rate, in accordancewith embodiments herein. At 602, the one or more processors monitor theheart rate. At 604, the one or more processors compare the current heartrate to a base heart rate that was logged when setting the paced andsensed AV delays as described herein (e.g., as set at 308 in FIG. 3, at404 or 410 in FIG. 4, or at 508 in FIG. 5). The processors determinewhether any change has occurred between the current heart rate and thebase heart rate. When a change occurs, the processors determine whetherthe change in the heart rate exceeds a threshold. For example, one ormore thresholds may be defined, such that small changes in heart rate donot warrant adjustment of the sensed and/or paced AV delays. When thechange in heart rate does not exceed the threshold, flow returns to 602.Alternatively, when the change in heart rate exceeds the threshold, theprocessors interpret this condition to indicate that the heart rate hassufficiently changed to indicate that the intrinsic AV interval hassimilarly changed and thus warrant a change in the programmed sensed andpaced AV delays. Accordingly, flow advances from 604 to 606.

At 606, the one or more processors determine a relationship between thecurrent heart rate and the base heart rate. For example, the ratio mayindicate a percentage increase or decrease in the current heart rateover the base heart rate. Optionally, the processors may determine therelationship in a manner other than a ratio. For example, therelationship may be defined as a difference between the current and baseheart rates, an average (or other mathematical combination) of thecurrent and base heart rates, and the like.

At 608, the one or more processors adjust lengths of the AVDs and AVDpbased on the relation between the current and base heart rates. Forexample, when the ratio of the current and base heart rates indicatethat the current heart rate is slower than the heart rate that waslogged when setting the prior AVDs and AVDp, the processorsautomatically extend the AVDs and AVDp in proportion to the ratio of thecurrent and base heart rates. For example, when the current heart ratefalls below a base heart rate by 10%, the AVDs and AVDp may be extendedsimilarly by 10%. Alternatively, when the current heart rate increasesto be faster than the logged heart rate, the processors mayautomatically shorten the AVDs and AVDp in proportion to the ratio ofthe current and base heart rates.

The embodiment of FIG. 6 enables dynamic adjustment of the AVDs and AVDpto automatically follow changes in the intrinsic AV interval thatinherently follow changes in heart rate (e.g., activity, relaxation).The embodiment of FIG. 6 avoids an undue delay, when the heart ratedrops (and AV interval lengthens), that may otherwise result (e.g., upto 3-5 min) in systems and methods that only check for longer AVintervals after an extended number of cardiac beats (e.g., every 256beats). Instead, the embodiment of FIG. 6 provides an automaticrate-responsive AVDs and AVDp adjustment when the heart rate reduces.Each time methods and systems herein reset/reprogram the AVDs and AVDpvalues, the current heart rate is logged as the new base heart rate. Asthat heart rate slows down, the AVDs and AVDp values are automaticallyextended in a linear fashion, until the next time re-measurement of theAV interval (e.g., up to 256 beats later).

Closing

The various methods as illustrated in the Figures and described hereinrepresent exemplary embodiments of methods. The methods may beimplemented in software, hardware, or a combination thereof. In variousof the methods, the order of the steps may be changed, and variouselements may be added, reordered, combined, omitted, modified, etc.Various of the steps may be performed automatically (e.g., without beingdirectly prompted by user input) and/or programmatically (e.g.,according to program instructions).

Various modifications and changes may be made as would be obvious to aperson skilled in the art having the benefit of this disclosure. It isintended to embrace all such modifications and changes and, accordingly,the above description is to be regarded in an illustrative rather than arestrictive sense.

Various embodiments of the present disclosure utilize at least onenetwork that would be familiar to those skilled in the art forsupporting communications using any of a variety ofcommercially-available protocols, such as Transmission ControlProtocol/Internet Protocol (“TCP/IP”), User Datagram Protocol (“UDP”),protocols operating in various layers of the Open System Interconnection(“OSI”) model, File Transfer Protocol (“FTP”), Universal Plug and Play(“UpnP”), Network File System (“NFS”), Common Internet File System(“CIFS”) and AppleTalk. The network can be, for example, a local areanetwork, a wide-area network, a virtual private network, the Internet,an intranet, an extranet, a public switched telephone network, aninfrared network, a wireless network, a satellite network and anycombination thereof.

In embodiments utilizing a web server, the web server can run any of avariety of server or mid-tier applications, including Hypertext TransferProtocol (“HTTP”) servers, FTP servers, Common Gateway Interface (“CGI”)servers, data servers, Java servers, Apache servers and businessapplication servers. The server(s) also may be capable of executingprograms or scripts in response to requests from user devices, such asby executing one or more web applications that may be implemented as oneor more scripts or programs written in any programming language, such asJava®, C, C # or C++, or any scripting language, such as Ruby, PHP,Perl, Python or TCL, as well as combinations thereof. The server(s) mayalso include database servers, including without limitation thosecommercially available from Oracle®, Microsoft®, Sybase® and IBM® aswell as open-source servers such as MySQL, Postgres, SQLite, MongoDB,and any other server capable of storing, retrieving and accessingstructured or unstructured data. Database servers may includetable-based servers, document-based servers, unstructured servers,relational servers, non-relational servers or combinations of theseand/or other database servers.

The environment can include a variety of data stores and other memoryand storage media as discussed above. These can reside in a variety oflocations, such as on a storage medium local to (and/or resident in) oneor more of the computers or remote from any or all of the computersacross the network. In a particular set of embodiments, the informationmay reside in a storage-area network (“SAN”) familiar to those skilledin the art. Similarly, any necessary files for performing the functionsattributed to the computers, servers or other network devices may bestored locally and/or remotely, as appropriate. Where a system includescomputerized devices, each such device can include hardware elementsthat may be electrically coupled via a bus, the elements including, forexample, at least one central processing unit (“CPU” or “processor”), atleast one input device (e.g., a mouse, keyboard, controller, touchscreen or keypad) and at least one output device (e.g., a displaydevice, printer or speaker). Such a system may also include one or morestorage devices, such as disk drives, optical storage devices andsolid-state storage devices such as random access memory (“RAM”) orread-only memory (“ROM”), as well as removable media devices, memorycards, flash cards, etc.

Such devices also can include a computer-readable storage media reader,a communications device (e.g., a modem, a network card (wireless orwired), an infrared communication device, etc.) and working memory asdescribed above. The computer-readable storage media reader can beconnected with, or configured to receive, a computer-readable storagemedium, representing remote, local, fixed and/or removable storagedevices as well as storage media for temporarily and/or more permanentlycontaining, storing, transmitting and retrieving computer-readableinformation. The system and various devices also typically will includea number of software applications, modules, services or other elementslocated within at least one working memory device, including anoperating system and application programs, such as a client applicationor web browser. It should be appreciated that alternate embodiments mayhave numerous variations from that described above. For example,customized hardware might also be used and/or particular elements mightbe implemented in hardware, software (including portable software, suchas applets) or both. Further, connection to other computing devices suchas network input/output devices may be employed.

Various embodiments may further include receiving, sending, or storinginstructions and/or data implemented in accordance with the foregoingdescription upon a computer-readable medium. Storage media and computerreadable media for containing code, or portions of code, can include anyappropriate media known or used in the art, including storage media andcommunication media, such as, but not limited to, volatile andnon-volatile, removable and non-removable media implemented in anymethod or technology for storage and/or transmission of information suchas computer readable instructions, data structures, program modules orother data, including RAM, ROM, Electrically Erasable ProgrammableRead-Only Memory (“EEPROM”), flash memory or other memory technology,Compact Disc Read-Only Memory (“CD-ROM”), digital versatile disk (DVD)or other optical storage, magnetic cassettes, magnetic tape, magneticdisk storage or other magnetic storage devices or any other medium whichcan be used to store the desired information and which can be accessedby the system device. Based on the disclosure and teachings providedherein, a person of ordinary skill in the art will appreciate other waysand/or methods to implement the various embodiments.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated embodiments thereofare shown in the drawings and have been described above in detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructionsand equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected,” when unmodified and referring to physical connections, isto be construed as partly or wholly contained within, attached to orjoined together, even if there is something intervening. Recitation ofranges of values herein are merely intended to serve as a shorthandmethod of referring individually to each separate value falling withinthe range, unless otherwise indicated herein and each separate value isincorporated into the specification as if it were individually recitedherein. The use of the term “set” (e.g., “a set of items”) or “subset”unless otherwise noted or contradicted by context, is to be construed asa nonempty collection comprising one or more members. Further, unlessotherwise noted or contradicted by context, the term “subset” of acorresponding set does not necessarily denote a proper subset of thecorresponding set, but the subset and the corresponding set may beequal.

Operations of processes described herein can be performed in anysuitable order unless otherwise indicated herein or otherwise clearlycontradicted by context. Processes described herein (or variationsand/or combinations thereof) may be performed under the control of oneor more computer systems configured with executable instructions and maybe implemented as code (e.g., executable instructions, one or morecomputer programs or one or more applications) executing collectively onone or more processors, by hardware or combinations thereof. The codemay be stored on a computer-readable storage medium, for example, in theform of a computer program comprising a plurality of instructionsexecutable by one or more processors. The computer-readable storagemedium may be non-transitory.

All references, including publications, patent applications and patents,cited herein are hereby incorporated by reference to the same extent asif each reference were individually and specifically indicated to beincorporated by reference and were set forth in its entirety herein.

It is to be understood that the subject matter described herein is notlimited in its application to the details of construction and thearrangement of components set forth in the description herein orillustrated in the drawings hereof. The subject matter described hereinis capable of other embodiments and of being practiced or of beingcarried out in various ways. Also, it is to be understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. While the dimensions, types ofmaterials and physical characteristics described herein are intended todefine the parameters of the invention, they are by no means limitingand are exemplary embodiments. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Thescope of the invention should, therefore, be determined with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled. In the appended claims, the terms“including” and “in which” are used as the plain-English equivalents ofthe respective terms “comprising” and “wherein.” Moreover, in thefollowing claims, the terms “first,” “second,” and “third,” etc. areused merely as labels, and are not intended to impose numericalrequirements on their objects. Further, the limitations of the followingclaims are not written in means-plus-function format and are notintended to be interpreted based on 35 U.S.C. § 112(f), unless and untilsuch claim limitations expressly use the phrase “means for” followed bya statement of function void of further structure.

What is claimed is:
 1. A method for dynamic device based AV delayadjustment, the method comprising: providing electrodes configured to belocated proximate to an atrial (A) site and a right ventricular (RV)site; utilizing one or more processors, in an implantable medical device(IMD), for: detecting an atrial paced (Ap) event or atrial sensed (As)event; determining a measured AV interval corresponding to an intervalbetween the Ap event or the As event and a ventricular sensed event;calculating a percentage-based (PB) offset based on the measured AVinterval; automatically dynamically adjusting an AV delay, utilized bythe IMD, based on the measured AV interval and the PB offset; andmanaging a pacing therapy, utilized by the IMD, based on the AV delayafter the adjusting operation.
 2. The method of claim 1, wherein thecalculating operation further comprises setting the PB offset to equal aprogrammed percentage of the measured AV interval, and wherein theadjusting operation further comprises setting the AV delay to correspondto a difference between the measured AV interval and the PB offset. 3.The method of claim 1, wherein the calculating and adjusting operationsfurther comprise setting the AV delay, in connection with the As event,as AVDs=[(As-Vs interval)−(PB offset)], wherein the PB offset=(As-Vsinterval)*P1%], the As-Vs interval corresponds to the measured AVinterval between the As event and a sensed ventricular (Vs) event, andthe P1% corresponds to a pre-programmed percentage.
 4. The method ofclaim 1, further comprising providing an electrode configured to beproximate to a left ventricular (LV) site, wherein the measured AVinterval comprises a measured A-RV interval and a measured A-LVinterval, the adjusting operation further comprising adjusting, as theAV delay: a delay associated with the As event to a right sensedventricular (RVs) event as A-RVDs=[(As-RVs interval)−(PBs-RV offset)],wherein the PBs-RV offset represents a first percentage based offsetbetween the As event and the RVs event; and a delay associated with theAs event to a left ventricular sensed (LVs) event as A-RVDs=[(As-LVsinterval)−(PBs-LV offset)], wherein PBs-LV offset represents a secondpercentage based offset between the As event and the LVs event.
 5. Themethod of claim 1, further comprising logging a base heart rateassociated with the measured AV interval.
 6. The method of claim 5,further comprising monitoring a current heart rate, and automaticallyrepeating the determining, calculating and adjusting operations when thecurrent heart rate changes by more than a predetermined thresholdrelative to the base heart rate.
 7. The method of claim 6, furthercomprising extending the AV delay in proportion to a ratio between thecurrent heart rate and the base heart rate when the current heart rateis slower than the base heart rate.
 8. The method of claim 1, furthercomprising extending the AV delay to correspond to a default search AVdelay (AVD_(search)); sensing cardiac activity for a predeterminednumber of cardiac beats; identifying whether the cardiac activity isindicative of a conduction block condition or non-conduction blockcondition; and repeating the determining, calculating and adjustingoperations only when the non-conduction block condition is identified.9. The method of claim 8, wherein the identifying operation comprisesidentifying the cardiac activity to be indicative of a conduction blockcondition when fewer than a select number of cardiac beats exhibitsensed ventricular events during the default search AV delayAVD_(search).
 10. The method of claim 1, wherein the adjusting comprisesadjusting a sensed AV delay (AVDs) and a paced AV delay (AVDp), themethod further comprising identifying a presence of conduction blockand, in response thereto, revert the AVDs and base AVDp to AVDs-base andAVDp-base programmed lengths, respectively; and maintaining the baseAVDp-base and AVDs-base programmed lengths for a select second number ofcardiac beats.
 11. An implantable medical device (IMD), comprising:electrodes configured to be located proximate to an atrial (A) site anda right ventricular (RV) site; memory to store program instructions; oneor more processors configured to implement the program instructions to:detect an atrial paced (Ap) event or atrial sensed (As) event; determinea measured AV interval corresponding to an interval between the Ap eventor the As event and a ventricular sensed event; calculate apercentage-based (PB) offset based on the measured AV interval;automatically dynamically adjust an AV delay, utilized by the IMD, basedon the measured AV interval and the PB offset; and manage a pacingtherapy, utilized by the IMD, based on the AV delay after the adjustingoperation.
 12. The device of claim 11, wherein the one or moreprocessors are configured to set the PB offset to equal a programmedpercentage of the measured AV interval, and set the AV delay tocorrespond to a difference between the measured AV interval and the PBoffset.
 13. The device of claim 11, wherein the one or more processorsare configured to perform the calculating and adjusting operations bysetting the AV delay, in connection with the As event, as AVDs=[(As-Vsinterval)−(PB offset)], wherein the PB offset=(As-Vs interval)*P1%], theAs-Vs interval corresponds to the measured AV interval between the Asevent and a sensed ventricular (Vs) event, and the P1% corresponds to apre-programmed percentage.
 14. The device of claim 11, furthercomprising an electrode configured to be proximate to a left ventricular(LV) site, wherein the measured AV interval comprises a measured A-RVinterval and a measured A-LV interval, the one or more processors toadjust the AV delay by adjusting, as the AV delay: a delay associatedwith the As event to a right sensed ventricular (RVs) event asA-RVDs=[(As-RVs interval)−(PBs-RV offset)], wherein the PBs-RV offsetrepresents a first percentage based offset between the As event and theRVs event; and a delay associated with the As event to a leftventricular sensed (LVs) event as A-RVDs=[(As-LVs interval)−(PBs-LVoffset)], wherein PBs-LV offset represents a second percentage basedoffset between the As event and the LVs event.
 15. The device of claim11, wherein the one or more processors are configured to log a baseheart rate associated with the measured AV interval.
 16. The device ofclaim 15, wherein the one or more processors are configured to monitor acurrent heart rate, and automatically repeat the determining,calculating and adjusting operations when the current heart rate changesby more than a predetermined threshold relative to the base heart rate.17. The device of claim 16, wherein the one or more processors areconfigured to extend the AV delay in proportion to a ratio between thecurrent heart rate and the base heart rate when the current heart rateis slower than the base heart rate.
 18. The device of claim 11, whereinthe one or more processors are configured to: extend the AV delay tocorrespond to a default search AV delay (AVD_(search)); sensing cardiacactivity for a predetermined number of cardiac beats; identify whetherthe cardiac activity is indicative of a conduction block condition ornon-conduction block condition; and repeat the determining, calculatingand adjusting operations only when the non-conduction block condition isidentified.
 19. The device of claim 18, wherein the one or moreprocessors are configured to perform the identifying operation byidentifying the cardiac activity to be indicative of a conduction blockcondition when fewer than a select number of cardiac beats exhibitsensed ventricular events during the default search AV delayAVD_(search).
 20. The device of claim 11, wherein the one or moreprocessors are configured to adjust a sensed AV delay (AVDs) and a pacedAV delay (AVDp), identify a presence of conduction block and, inresponse thereto, revert the AVDs and base AVDp to AVDs-base andAVDp-base programmed lengths, respectively; and maintain the baseAVDp-base and AVDs-base programmed lengths for a select second number ofcardiac beats.